browser_press_key · Byob MCP: Risk & Policy

WHAT IT DOES

What browser_press_key does on Byob

AI agents invoke browser_press_key to trigger actions in Byob. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why browser_press_key needs a policy

This tool triggers browser actions by sending keyboard events to a real Chrome browser session. Keyboard events can trigger form submissions (Enter), navigation, UI interactions, and other operations whose effects depend on the current page state and key sent. This constitutes executing external operations in a live browser, warranting the Execute category.

From the tool's definition 'Send a single keyboard event to the page (e.g. Enter, Escape, Tab, F5, ArrowDown'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

browser_press_key Rate-limited

browser_press_key stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "browser_press_key": {
      "limits": [
        {
          "counter": "browser_press_key_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Byob, so you can run agents against it safely.

FAQ

Questions about browser_press_key

What does the browser_press_key tool do? +

Send a single keyboard event to the page (e.g. Enter, Escape, Tab, F5, ArrowDown,. It is categorised as a Execute tool in the Byob MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on browser_press_key? +

Register the Byob MCP server in PolicyLayer and add a rule for browser_press_key: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Byob. Nothing to install.

What risk level is browser_press_key? +

browser_press_key is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit browser_press_key? +

Yes. Add a rate_limit block to the browser_press_key rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block browser_press_key completely? +

Set action: deny in the PolicyLayer policy for browser_press_key. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides browser_press_key? +

browser_press_key is provided by the Byob MCP server (wxtsky/byob). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.